Best spoiler (Purpose not looks):Pling:

[ilicos]

Plus the original spoiler isn't to add downforce. Its to stabilise the car under high speed braking.

 

I think the TRD definately gives more downforce looking at the angle of attack and shape of the wing.

 

I recall that above 90mph it adds 100kg of downforce?

[Dnk]

I recall that above 90mph it adds 100kg of downforce?

 

What the thread needs is some factual figures, can you recall where you got that info from ?

[jagman]

To measure downforce you simply fit pressure sensors , piezo or strain guage and go for a drive , then repeat on the other spoiler.

Max angle just over 14 degrees then the wing stalls

The upper surface is the lower wing surface;)

[Chris Wilson]

Hire the wind tunnel at MIRA, every week in Racecar Engineering they have a project car in the tunnel and run through some basic tests to illustrate things an amateur aerodynamicist can do to optimise his car. They have had case studies from Minis to late F1's featured. Plenty of people on here have spent more on shiny things than a day at MIRA might cost You even get a bit of help from the professionals that run the tunnel, so you aren't just *issing in the wind.

[TLicense]

Max angle just over 14 degrees then the wing stalls

 

That's very specific, and I've no doubt correct for 'a' wing, but is unlikely to be the stall angle for either the stock or TRD wing.

 

For instance, we have some wings that can run up to 30 degrees of incidence, whereas we have others that stall at 15 degrees.

 

But yes, your method of installing load cells at the base of the wing is the most scientific method, and the same as we use.

You can also fit linear potentiometers between both ends of the suspension dampers which if you know how much load causes how much displacement can be used to determine downforce. The only difficulty is that the car needs to be travelling over a perfectly flat surface to accurately get any data from it.

 

As Chris says though, these tests would be best done at Mira, but no-one here will pay to put a car there, and to be fair it's still a little bit heath robinson there. (No moving ground, no motion control system...)

[Dnk]

That's very specific, and I've no doubt correct for 'a' wing, but is unlikely to be the stall angle for either the stock or TRD wing.

 

For instance, we have some wings that can run up to 30 degrees of incidence, whereas we have others that stall at 15 degrees.

 

But yes, your method of installing load cells at the base of the wing is the most scientific method, and the same as we use.

You can also fit linear potentiometers between both ends of the suspension dampers which if you know how much load causes how much displacement can be used to determine downforce. The only difficulty is that the car needs to be travelling over a perfectly flat surface to accurately get any data from it.

 

As Chris says though, these tests would be best done at Mira, but no-one here will pay to put a car there, and to be fair it's still a little bit heath robinson there. (No moving ground, no motion control system...)

 

Can you borrow some load cells

[TLicense]

I was meaning a rear diffuser if that wasn't very clear.

 

Do you agree that there is an area of low pressure behind the car when it is traveling at speed? If so, then you should believe that increasing that pressure in relation to the pressure at the front of the car will cause a frontward force (well, really it's causing less of a pulling force) to act on the car due to the lower difference in pressure? This means the car has to use less fuel to travel at any speed.

 

Another way to think of it would be like wind acting on a car, wind hitting the front of the car would cause a force to be acting on the car, pushing it backwards, yes? And wind hitting the rear of the car would cause a force to act forward on the car? Same principle here, if there is less vacuum pulling the car backwards (i.e. more 'force' pushing it forwards), the car will use less fuel.

 

That's what a properly set-up rear diffuser is made to do, funnel air into the low pressure area behind the car to reduce drag, while at the same time the fast-moving air underneath the car will create a low-pressure are which will pull the car down.

 

But you're forgetting that the diffuser itself is expanding the flow, and that flow is slowing down as it does. Trust me, in the decade that I've been designing amongst other things diffusers for many race-cars, not one would have created less drag overall than not having a diffuser at all. To give you an idea, I recon I've probably drawn and tested over a thousand different diffuser configurations if not more.

Case in point, a couple of years ago the FIA reduced the size of the diffuser we were allowed on the race-cars. This was a drag benefit. We didn't gain more drag by having smaller diffusers we lost it. At the same time we lost a crap-load of downforce which was the point of the operation. We've got even smaller diffusers for next year, so I'll let you draw your own conlusions as to how that will effect the cars.

 

I've written a thread on how diffusers work that's on here somewhere, you might find it enlightening.

[TLicense]

Can you borrow some load cells

 

I can design and manufacture some. Would be about £2000 a piece.

Pretty cheap to be honest, as when I was at Williams, we bought a 6 component loadcell for £120,000. Was a nice bit of kit though.

[Animal]

Totally off topic, but did you know a Mick Threlfall at Williams? He's a sound engineer in his spare time and runs the FOH mixing desk for most of the gigs we put on.

[Chris Wilson]

I would think linear potentiometers linking the shell to the rear suspension would be the cheapest real time means of measuring downforce with any degree of accuracy unless laser ride height sensors have become cheaper in recent years? I am about to take the diffuser off my Zeus and it has some interesting dust marks in the oil film from a spill when changing an oil line, could you look at it and see what it says to you, Tony, if I take a pic later? Ta!

[Wez]

I am about to take the diffuser off my Zeus and it has some interesting dust marks in the oil film from a spill when changing an oil line, could you look at it and see what it says to you, Tony, if I take a pic later? Ta!

 

They use some lumi paint in F1 for similar testing

[Dnk]

I am about to take the diffuser off my Zeus and it has some interesting dust marks in the oil film from a spill when changing an oil line, could you look at it and see what it says to you, Tony, if I take a pic later? Ta!

 

CLEAN ME ? i'll get my coat

[steady_dave]

Wow this is getting quite serious. I like it!!!!!

[TLicense]

I would think linear potentiometers linking the shell to the rear suspension would be the cheapest real time means of measuring downforce with any degree of accuracy unless laser ride height sensors have become cheaper in recent years? I am about to take the diffuser off my Zeus and it has some interesting dust marks in the oil film from a spill when changing an oil line, could you look at it and see what it says to you, Tony, if I take a pic later? Ta!

 

Laser ride height sensors are still about £2500 a piece for a decent one.

We actually have a number of them here that we can't use as they were made obsolete as the new ones now used digital rather than analogue outputs and the company that supplies all our hardware no-longer supported the analogue version of the main controller that they plugged into.

 

Send the pic over. I can't say that it will make much sense to me either, but I'll give it a go.

[Morpheus]

Ok, since my previous highly accurate and reliable idea (again, if done properly) has been dismissed in favour of ultimately more expensive options, how about attaching DRO's (digital readouts normally used for milling machines) to the shocks or suspension arms somewhere, as per linear potentiometer suggestion? Same thing really but you have an LCD readout of the exact distance travelled.

 

No need for computers or calibration either, except for the initial weight loading at various values to set min/max expected range at a given load. You'll obviously get an exponential dataset though, to calibrate.

 

The reason this would be unsuitable compared to my previous suggestion, is obviously high speed oscillation and vibration (which cheap DRO's are not good at) and having two independent readouts to average. Also, tough to operate but they do have output jacks.

 

Alternatively, you could have a trailing wheel on a sprung arm with potentiometer, inclinometer etc. attached.

 

Maybe something as simple as an inclinometer mounted on the passenger seat headrest! They're accurate to minutes if not seconds. Good enough to see which spoiler/wing is best.

 

Even scales like protractors attached to the rear subframe and a fixed pointer on a link arm or wishbone. Again you'd need a camera but it's very cheap and easy to do.

 

Mr. Dunk Sir, weight added to the (inside) boot is for calibration only and obviously can take any form desired as long as it's accurate. I'm not asking anyone to dump bags of cement on the car.

 

I think if the point is to find out which one is more effective 'scientifically' (an often misunderstood concept if ever there was one!) just timing both units on the same car up to a given speed on the same stretch of road should prove that, if lift simply equals drag and manufacturers have been fitting them for decades purely for downforce (negative lift) instead of reducing drag.

 

I think not but whatever, just choose a hot, sunny day with no changeable wind and swap them as fast as possible to keep things even. The slowest time should be the highest downforce; or should it........?

Edited July 6, 2010 by Morpheus (see edit history)

[Dnk]

What are you smoking mate ? it must be good

 

I think youd be better off with some digital scales in the boot somehow attached to the tailgate, with the tailgate open but lowered onto some foam and race taped so it couldnt fly up then as speed increases so the pressure pushing the tailgate down goes up giving a reading on the scales.

 

Job done lol

[Morpheus]

What are you smoking mate ? it must be good

 

I think youd be better off with some digital scales in the boot somehow attached to the tailgate, with the tailgate open but lowered onto some foam and race taped so it couldnt fly up then as speed increases so the pressure pushing the tailgate down goes up giving a reading on the scales.

 

Job done lol

 

That was too obvious for me to even say!

 

Seriously though, that's a pretty good idea actually! I mean, you wouldn't need much of a gap or lift in the tailgate and a passenger could lean round and read the scales, perhaps via a mirror or two or just film it on camcorder/phone and shout "Now!" when you get to 90mph!

 

Digital scales require virtually no movement to get a reading as they're piezoelectric linear stress stretchy thingybob whatchamacallits and highly accurate too. You can also 'tare' (account for) the weight of the door.

 

Job done indeed!

Edited July 6, 2010 by Morpheus
Typo (see edit history)

[Dnk]

That was too obvious for me to even say!

 

Seriously though, that's a pretty good idea actually! I mean, you wouldn't need much of a gap or lift in the tailgate and a passenger could lean round and read the scales, perhaps via a mirror or two or just film it on camcorder/phone and shout "Now!" when you get to 90mph!

 

Digital scales require virtually no movement to get a reading as they're piezoelectric linear stress stretchy thingybob whatchamacallits and highly accurate too.

 

Job done indeed!

 

Glad you like it, i wonder if i can borrow my old race teams corner weight scales, they have a seperate readout which could sit on the passenger seat

[Morpheus]

You do realise Steady Dave, that the fastest Supras don't even use spoilers or wings and they're perfectly stable at 250mph. Still interesting to come up with ideas though; keeps the brain active!

 

These any good? Wouldn't know how to connect them though but for a tenner?!!

 

http://cgi.ebay.co.uk/4-Pack-Load-Cells-NEW-100kg-TY2006LS-/330449164081?cmd=ViewItem&pt=UK_Measuring_Tools_Levels&hash=item4cf04e1731

 

Got it! Perfect! Might buy one anyway but 100g increments. Good enough for spoilers! You could even mount the spoilers/wings on ply and use a fixed fan like at a rolling road or make a jet engine with an old turbo.....or, or....

 

http://cgi.ebay.co.uk/Jship-150kg-digital-platform-scale-postal-parcel-150-kg-/190410541219?cmd=ViewItem&pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2c555a48a3

Edited July 6, 2010 by Morpheus
Additional info. (see edit history)

[steady_dave]

This is amazing, I may try the scales idea, now, can I borrow a TRD spoiler....

[Dnk]

 

Got it! Perfect! Might buy one anyway but 100g increments. Good enough for spoilers! You could even mount the spoilers/wings on ply and use a fixed fan like at a rolling road or make a jet engine with an old turbo.....or, or....

 

 

 

lmao, i see your smoking again have you ever seen a windtunnel ?

 

You really need the test done on the car to get the same aiflow that actually goes over the car.

[bodilx6]

You do realise Steady Dave, that the fastest Supras don't even use spoilers or wings and they're perfectly stable at 250mph.

 

But they are driving a completely straight line, right?

Remember the old Audi TT's that flew off the Autobahn when passing 120mph or so in sweepers?

 

- that alone makes me bolt on the wing each time I go down there..

[steady_dave]

You do realise Steady Dave, that the fastest Supras don't even use spoilers or wings and they're perfectly stable at 250mph. QUOTE]

 

My car is limited to 112MPH, and can't actually recall asking which spoiler/wing would be better for a standing mile run.

[Morpheus]

lmao, i see your smoking again have you ever seen a windtunnel ?

 

You really need the test done on the car to get the same aiflow that actually goes over the car.

 

 

Hence my original idea.........though wind direction and strength would need to be very low or constant, on car, hence again suggesting to do it on a high pressure day for repeatability.

 

Being 'creative' comes naturally btw, thanks, though I did get a bang on the head once......

[Morpheus]

But they are driving a completely straight line, right?

Remember the old Audi TT's that flew off the Autobahn when passing 120mph or so in sweepers?

 

- that alone makes me bolt on the wing each time I go down there..

 

Audi TT's had a rounded rear end which caused the lift and instability until they were forced to add a lip. Same with the Elise. Supras already have one in the rear door.

 

That reminds me, when's the next Nerd Buggering trip?

 

Never been! Infact, never even bought the sticker saying never been!

Edited July 7, 2010 by Morpheus (see edit history)